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App Dev Worksheet: Events

App development lesson 17: Events: on tap, do this · Set 295 · 40 questions
TalentJR

Developer's tip (When this, do that): Event → handler → action: “on tap, do this”. The handler runs once for every tap. Counter: start + taps × step. A limit stops it growing; on = !on flips ON / OFF.

NameDateTime takenScore ___ / 40
  1. 1.👆 The user taps the button 3 times. What does the label show now?
    let on = false;
    button.onTap = function () {
      on = !on;
      if (on) {
        label.text = "ON";
      } else {
        label.text = "OFF";
      }
    };     (a) ON (b) OFF
  2. 2.👆 What kind of event is this: the screen first opens? (a) a load event (b) a timer event (c) a text event (d) a tap event
  3. 3.👆 What kind of event is this: the user types a letter? (a) a timer event (b) a tap event (c) a load event (d) a text event
  4. 4.True or false: the user presses Save is a timer event. (a) False (b) True
  5. 5.👆 The user taps the button 3 times. What number does the label show now?
    let coins = 0;
    button.onTap = function () {
      coins = coins + 4;
      label.text = coins;
    };
  6. 6.👆 The user taps the button 2 times. What number does the label show now?
    let points = 7;
    button.onTap = function () {
      points = points + 1;
      label.text = points;
    };
  7. 7.👆 The user taps the button 4 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 4) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  8. 8.👆 The user taps the button 5 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  9. 9.👆 The user taps the button 5 times. What does the label show now?
    let on = false;
    button.onTap = function () {
      on = !on;
      if (on) {
        label.text = "ON";
      } else {
        label.text = "OFF";
      }
    };     (a) OFF (b) ON
  10. 10.👆 What kind of event is this: one second passes? (a) a text event (b) a timer event (c) a load event (d) a tap event
  11. 11.True or false: the user types a letter is a text event. (a) True (b) False
  12. 12.👆 The user taps the button 5 times. What number does the label show now?
    let points = 8;
    button.onTap = function () {
      points = points + 2;
      label.text = points;
    };
  13. 13.👆 Which of these is an event? (a) the font size (b) the user taps a button (c) the icon colour (d) a list of names
  14. 14.👆 What kind of event is this: the search box changes? (a) a tap event (b) a timer event (c) a load event (d) a text event
  15. 15.👆 A tap handler runs how many times if the user taps 4 times? (a) 4 (b) 0 (c) 8 (d) 1
  16. 16.👆 The user taps the button 3 times. What number does the label show now?
    let coins = 7;
    button.onTap = function () {
      coins = coins + 2;
      label.text = coins;
    };
  17. 17.👆 The user taps the button 2 times. What does the label show now?
    let on = false;
    button.onTap = function () {
      on = !on;
      if (on) {
        label.text = "ON";
      } else {
        label.text = "OFF";
      }
    };     (a) ON (b) OFF
  18. 18.👆 The user taps the button 3 times. What number does the label show now?
    let score = 10;
    button.onTap = function () {
      score = score + 3;
      label.text = score;
    };
  19. 19.👆 The user taps the button 7 times. What does the label show now?
    let on = false;
    button.onTap = function () {
      on = !on;
      if (on) {
        label.text = "ON";
      } else {
        label.text = "OFF";
      }
    };     (a) OFF (b) ON
  20. 20.👆 An event in an app is ___. (a) a kind of list (b) something that happens (c) an app store (d) a colour theme
  21. 21.👆 The user types Kabir in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hello, " + nameBox.text + "!";
    };     (a) Hello, Kabir! (b) Hello, nameBox.text! (c) Hello! (d) Kabir
  22. 22.👆 The user types Riya in nameBox and taps the button 1 time. What does the label show?
    button.onTap = function () {
      label.text = "Hi, " + nameBox.text + "!";
    };     (a) Hi, nameBox.text! (b) Hi, Riya! (c) Hi! (d) Riya
  23. 23.👆 The user taps the button 6 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 4) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  24. 24.👆 The user taps the button 1 times. What does the label show now?
    let on = false;
    button.onTap = function () {
      on = !on;
      if (on) {
        label.text = "ON";
      } else {
        label.text = "OFF";
      }
    };     (a) ON (b) OFF
  25. 25.👆 Code that runs when an event happens is called a ___. (a) hashtag (b) handler (c) headline (d) header
  26. 26.👆 The user taps the button 1 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 4) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  27. 27.👆 The user taps the button 6 times. What number does the label show now?
    let coins = 10;
    button.onTap = function () {
      coins = coins + 1;
      label.text = coins;
    };
  28. 28.👆 The user taps the button 1 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  29. 29.👆 “On tap → do this” links an event to ___. (a) a font (b) a charger (c) an action (d) a web address
  30. 30.👆 The user taps the button 2 times. What number does the label show now?
    let coins = 0;
    button.onTap = function () {
      coins = coins + 1;
      label.text = coins;
    };
  31. 31.👆 The user taps the button 4 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 3) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  32. 32.True or false: the user presses Save is a tap event. (a) False (b) True
  33. 33.True or false: the user types a letter is a tap event. (a) False (b) True
  34. 34.👆 The user taps the button 5 times. What number does the label show now?
    let points = 1;
    button.onTap = function () {
      points = points + 1;
      label.text = points;
    };
  35. 35.👆 The user taps the button 2 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 5) {
        likes = likes + 1;
      }
      label.text = likes;
    };
  36. 36.True or false: a countdown hits zero is a timer event. (a) True (b) False
  37. 37.True or false: the user types a letter is a load event. (a) True (b) False
  38. 38.True or false: a finger hits Like is a text event. (a) False (b) True
  39. 39.👆 The user taps the button 6 times. What number does the label show now?
    let score = 0;
    button.onTap = function () {
      score = score + 4;
      label.text = score;
    };
  40. 40.👆 The user taps the button 7 times. What number does the label show now?
    let likes = 0;
    button.onTap = function () {
      if (likes < 2) {
        likes = likes + 1;
      }
      label.text = likes;
    };

Answer key

  1. ON
  2. a load event
  3. a text event
  4. False
  5. 12
  6. 9
  7. 4
  8. 3
  9. ON
  10. a timer event
  11. True
  12. 18
  13. the user taps a button
  14. a text event
  15. 4
  16. 13
  17. OFF
  18. 19
  19. ON
  20. something that happens
  21. Hello, Kabir!
  22. Hi, Riya!
  23. 4
  24. ON
  25. handler
  26. 1
  27. 16
  28. 1
  29. an action
  30. 2
  31. 3
  32. True
  33. False
  34. 6
  35. 2
  36. True
  37. False
  38. False
  39. 24
  40. 2

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